Diagnosis: Lung Histology
• Ciliated respiratory epithelial cells are seen in conducting airways from trachea to conducting bronchioles and are protective as well as provided motion of mucous via the mucociliary elevator/beating of cilia.
• Goblet cells are mucous secreting cells seen in trachea and bronchi, but not distal to these.
• The conducting bronchioles lack cartilage and are lined by respiratory epithelium—ciliated cells and basal reserve cells.
• Respiratory bronchioles are lined by Clara cells. These TTF-1 positive cells produce a component of surfactant, and secretions with antioxidant and antimicrobial properties. The Clara cell also has a role in detoxification of toxins.
• Alveolar ducts and alveoli are lined by type 1 and type 2 pneumocytes. Type 1 cells have specialized structure to maximize gas exchange (thin and fused to the endothelial cell of the capillaries); these cells are terminally differentiated. Type II pneumocytes are the reserve cell of the alveoli and produce essential components of surfactant.
